1. Field
The present disclosure relates generally to a transformer rectifier unit. More particularly, the present disclosure relates to a transformer rectifier unit configured to create a dual-polarity direct current power supply in response to receiving six alternating currents having six different phases.
2. Background
Some devices may be powered using direct current (DC) power, while other devices may be powered using alternating current (AC) power. Some electrical systems may convert alternating current into direct current to provide a source of direct current power. In alternating current, the flow of electrical charge reverses direction periodically. The waveform of alternating current is typically an alternating waveform such as, for example, a sine wave. In direct current, the flow of electrical charge is unidirectional.
As one illustrative example, in certain aircraft applications, alternating current received from an alternating current power supply is used to provide direct current to one or more electrical components on the aircraft. The alternating current power supply may take the form of, for example, without limitation, an alternator, a generator, an auxiliary power unit, an engine, or some other type of power supply. The one or more electrical components supplied with the direct current may include, for example, without limitation, a locking mechanism, a motor, a computer system, a light system, or some other type of electrical component, device, or system on the aircraft.
A transformer rectifier unit (TRU) may be used to convert alternating current received from an alternating current power supply into direct current to form a direct current power supply. In one illustrative example, the output voltage of the alternating current power supply may have a first magnitude. In this example, the output voltage of the direct current power supply may be a dual-polarity output voltage having a second magnitude. The dual-polarity output voltage includes a positive voltage and a negative voltage, both of the second magnitude. The second magnitude of the dual-polarity output voltage may be higher or lower than the first magnitude of the output voltage of the alternating current power supply, depending on the implementation.
However, in some cases, noise is present in the dual-polarity output voltage of the direct current power supply formed by the transformer rectifier unit. This noise is typically carried in the common mode of the direct current power supply. In particular, the noise may be seen as a ripple in the common mode voltage of the direct current power supply. This ripple may be referred to as a common mode voltage ripple. The common mode voltage of the direct current power supply is one-half of the vector sum of the positive and negative voltages of the dual-polarity output voltage of the direct current power supply. Reducing the common mode voltage reduces undesired noise in the dual-polarity output voltage of the direct current power supply.
Some currently available transformer rectifier units use a common mode choke to reduce the common mode voltage below a selected threshold to reduce the noise in the dual-polarity output voltage of the direct current power supply. The common mode choke may be a configuration comprised of one or more capacitors, one or more resistors, one or more other electrical components, or some combination thereof. However, using a common mode choke may increase the weight and cost of the transformer rectifier unit more than desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.